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Table Of Contents

EyeComfort white paper0F
- Scientific Background
  - 1. Flicker and Stroboscopic effect
  - 2. Photobiological safety

EyeComfort white paper

Nowadays, light quality is a key differentiator in lighting. In general, quality of light refers to the visual

aspects of light and its dependencies on and interaction with people and the environment. LEDification

gives us endless possibilities to differentiate in spatial, spectral, and temporal light quality. It forces us to

revise our traditional way of evaluating light quality. Signify continuously optimizes its products by

bringing together in-depth understanding of user needs, lighting application knowledge, and scientific

insights. Signify, the global leader in lighting, brings its LED lamps and LED luminaires to the market

under the well-known Philips brand.

Signify has created the EyeComfort trademark based on the following selected criteria: Flicker,

Stroboscopic effect, Photobiological safety, Glare, Dimming, Tunable, Color rendering, and Audible

noise.

Our LED lamps and LED luminaires product portfolio is evaluated using these criteria. This white paper

explains these criteria and, accordingly the importance of optimizing lighting.

Scientific Background

Philips branded EyeComfort LED of Signify incorporates the above-mentioned criteria:

1. Flicker and Stroboscopic effect

Flicker and Stroboscopic effect are Temporal Light Artifacts (“TLAs”). TLAs are defined as change in visual

perception, induced by a light stimulus, the luminance or spectral distribution, which fluctuates with

time for a human observer in a specified environment. Flicker is the perception of visual unsteadiness

induced by a light stimulus, the luminance or spectral distribution, which fluctuates with time, for a

static observer in a static environment. In other words, it is a disturbing rapid fluctuation of the light in

the room.

The stroboscopic effect is different than flicker and is defined as the change in motion perception,

induced by a light stimulus, the luminance or spectral distribution, which fluctuates with time, for a

static observer in a non-static environment. In other words, the stroboscopic effect results in an

unnatural break-up of a continuous motion.

A property of LEDs is the rapid response to variations in the input signal. Therefore, they faithfully

reproduce those fluctuations in the light output, potentially leading to TLAs for individuals in the lit

space. The fluctuations may come from various sources, including: disturbances on the mains,

interactions with controls (e.g. dimmers), disturbance on the input signal from external sources (e.g.

microwave), and designed-in fluctuations from the electronic driver. Methods to suppress fluctuations

in the light output of LEDs and, at the same time, lower the visibility of unwanted TLAs are known. These

methods, however, require compromise on cost and efficiency and require more physical space, while

lowering the lifetime of LED products with any architecture.

EyeComfort white paper may be amended by Signify as (additional) information becomes available to us in

various areas, including Product Development, Research, Standards & Regulations.

Summary of content (8 pages)

PAGE 1
EyeComfort white paper1 Nowadays, light quality is a key differentiator in lighting. In general, quality of light refers to the visual aspects of light and its dependencies on and interaction with people and the environment. LEDification gives us endless possibilities to differentiate in spatial, spectral, and temporal light quality. It forces us to revise our traditional way of evaluating light quality.
PAGE 2
Until recently, several measures like Flicker Index (FI) and Modulation depth were used to assess the visibility of flicker and the stroboscopic effect. None of these measures are suitable to predict what people actually perceive or experience. Flicker and stroboscopic effect visibility are impacted by modulation depth, frequency, wave shape and duty cycle, and these measures do not take into account all these parameters.
PAGE 3
The key scientific findings are [15]: - - With respect to the blue light hazard, LED lamps are no different from conventional technologies, such as incandescent and fluorescent lights. The portion of blue in LED lighting is not different from the portion in other technologies at the same color temperature. A comparison of LED retrofit products with the conventional products they are intended to replace, reveals that the risk levels are very similar and well within the uncritical range.
PAGE 4
luminance maps of the room to assess discomfort glare [34]. The last approach is identical to the TLA measures which are also based on modelling of the human visual system. For consumer lamps there is currently no glare measure available to quantify glare. Moreover, the perceived glare of a light bulb will also depend on the application. A naked bulb above the table close to the observer, and at eye height, will be more glary than the same bulb in a lampshade in the corner of the room.
PAGE 5
does not change during dimming. So, the incandescent bulb gives you both an intensity and color temperature variation, while LED only provides an intensity variation and the color temperature will remain the same. People appreciate the warm setting at low light levels for creating nice and cozy ambiances [45], but this can be different per region. Some Philips branded EyeComfort LEDs of Signify provide the WarmGlow dimming feature.
PAGE 6
7. Noise LEDs can suffer from audible noise, specifically when used at deep dimming levels. The voltages and current which are produced, can create mechanical resonance in the components. This noise can be perceived as very annoying and uncomfortable. This is the reason why Energy Star has put requirements in to place for audible noise levels. According to the Energy Star requirements for audible noise, lamps shall not emit noise above 24 dBA @ 1 meter distance [51].
PAGE 7
[19] EBERBACH, K. (1974). Der Einfluss der Leuchtdichtestruktur von Lichtquellen auf die Blendempfindung. Lichttechnik 6, p. 283–286. [20] WATERS, C.E., MISTRICK, R.G., BERNECKER, C.A. (1995): Discomfort Glare from Sources of Nonuniform Luminance. In: Journal of the Illuminating Engineering Society 24 (2), p. 73–85. [21] KASAHARA, T., AIZAWA, D., IRIKURA, T., MORIYAMA, T., TODA, M., IWAMOTO, M. (2006): Discomfort Glare Caused by White LED Light Source. In: Journal of Light and Visual Environment 30 (2), p.
PAGE 8
[39] CHEN, M.K, CHOU, C.J., CHEN H.S. (2016): Assessment of glare rating from non-uniform light sources. Proceedings of CIE 2016 “Lighting Quality and Energy Efficiency”, Melbourne, Australia, p. 697– 703. [40] TASHIRO T., KIMURA-MINODA, T., KOHKO, S., ISHIKAWA, T., AYAMA, M. (2011): Discomfort Glare Evaluation to White LEDs with Different Spatial Arrangement. Proceedings of the 27th Session of the CIE, Sun City, South Africa, p. 583–588. [41] SCHEIR, G.H., HANSELAER, P., BRACKE, P., DECONINCK, G.